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</o:shapelayout></xml><![endif]--></head><body lang=EN-NZ link=blue vlink=purple><div class=WordSection1><div><p class=MsoNormal>> As you may see, your .th2 file include only those three stations (and sketch). Probably it is bug in Therion that it not allows to hide stations from the final output. I may imagine the reason - <span style='background:yellow;mso-highlight:yellow'>MetaPost works with one scrap in time to interpret and draw that particular scrap. When it has nothing in scrap it will produce error</span>.<o:p></o:p></p></div><div><p class=MsoNormal><o:p> </o:p></p></div><div><p class=MsoNormal>> symbol-hide group cave-centerline will cause an error, because there is then no scrap to draw (Therion must have at least a scrap or a centreline to draw – seems that scrap station points and images don’t count).<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>I think it is a bug. If the user hides all of the centreline objects, and also hides all scrap objects (or something like that), then Therion should trap the error and exit in a controlled manner, rather than letting metapost get in a tangle and produce a mess of messages until it finally crashes.<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>Thanks for your insights Benoit, I had not thought of your approaches and they helped me make some mental connections. I guess redefining metapost for ‘area dimensions’ is the same as specifying ‘walls off’ in the survey file.<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>Bruce<o:p></o:p></p></div></div></body></html>